Apparatus for hot-stretching of synthetic filaments

ABSTRACT

AN APPARATUS FOR THE HOT-STRETCHING OF SYNTHETIC FILAMENTS WHEREIN THE HEATING OF THE FILAMENTS DURING THE STRETCHING OPERATION IS PROVIDED BY HEATING PLATES ATTACHED TO THE EXTERIOR SURFACE OF A HEATING TANK WHICH CONTAINS A HEATING MEDIUM MAINTAINED AT A UNIFORM AND CONSTANT TEMPERATURE.

Jan. 5, 1971 Y L HN 3,551,97!

APPARATUS FOR HOT-STRETCHING OF SYNTHETIC FILAMENTS Filed June 25, 1968 2 Sheets-Sheet 1 INVENTOR.

KARL A E/f/VEf? APPARATUS FOR HOT- 2 Sheets-Sheet 2 Filed June 25, 1968 INVENTOR.

KARL LEH/VER United States Patent US. Cl. 28-713 1 Claim ABSTRACT OF THE DISCLOSURE An apparatus for the hot-stretching of synthetic filaments wherein the heating of the filaments during the stretching operation is provided by heating plates attached to the exterior surface of a heating tank which contains a heating medium maintained at a uniform and constant temperature.

BACKGROUND OF THE INVENTION The present invention relates to apparatus for hotstretching synthetic filaments, the apparatus having a number of plates which can be heated and which are disposed between feed-roller groups and take-up roller groups and over which the filaments will pass.

To increase the mechanical strength of synthetic filaments, it is conventional to give the same a stretching treatment in which the filaments are stretched to several times their original length; during this operation, of course, molecular orientation is produced. The stretching treatment is usually carried out in what is known as a stretching zone of the apparatus, between two roller groups rotating at different speeds from one another. To further assist the stretching step, the filaments are passed over electrically heated plates, known as irons, in the stretching zone between the two roller groups. The irons most commonly used comprise a substantially vertical elongated metal plate comprising a slightly convex smooth running surface, or runway, for the filaments and an electric heating means which contacts the plate on the side opposite the runway. Most of the stretching usually occurs while the filaments are passing over the plate.

Modern stretch-twisting machines, which are used, inter alia, for hot-stretching synthetic filaments, have a number of plates of this kind so that a large number of filaments can be stretched simultaneously in side-by-side relationship. To ensure that the various filaments running over the plates are all of uniform quality, the temperature and surface texture of the various plates must remain identical during the stretching step. Unfortunately, with the plates of the prior art, even a very heavy outlay and special facilities provide only an unsatisfactory solution. If the number of plates used is large, it is impossible to ensure that all the plates are at the same temperature. Also, the temperature controllers and temperature supervisory facilities required for this purpose would increase costs and make the apparatus of doubtful economic viability. Another factor to be considered is that the working life of each runway is limited and the runways of the various plates wear very differently, with the result that the various plates, and therefore the filaments, become very dissimilar.

It is accordingly, an object of the invention to provide an apparatus for stretching synthetic filaments which maintains a uniform temperature in a very simple way at all the stretching stations, and which is of simple construction and requires very little servicing.

Other objects of the invention can be gathered from a reading of the following disclosure.

Patented Jan. 5, 1971 ICC SUMMARY OF THE INVENTION According to the present invention, there is provided apparatus for hot-stretching synthetic filaments, the apparatus having a number of heatable plates which are disposed between feed-roller groups and take-up roller groups and over which the filaments will pass, the plates being secured to a heatable horizontal tank and in contact with the tank surface.

In accordance with the invention, a number of independent irons having separate heating facilities and temperature control facilities are replaced by a heating tank which has plates mounted on its exterior surface, and which in practice requires just a single heating facility and just a single temperature control facility and which enables a number of plates to be heated uniformly and simultaneously. The plates can be produced from a metal strip having on one side a surface of the kind required for stretching operation. The strip is cut to lengths to suit requirements for the stretching operation and the lengths are secured to the tank. The strips then operate in the same way as the plates of the prior art constructions.

Preferably, the tank is filled with a liquid heating agent or medium. This feature enables the temperature at the various stretching stations formed by the plates to be kept constant quite readily. In its simplest form, which is nevertheless very advantageous for the required purpose, the tank can be produced from rectangular steel tubing.

To ensure that the filaments make intimate contact with the plate runways, the tank surface or wall on which the plates are disposed in convex at least at the places where the plates are disposed. The plates are prefabricated, by bending, to have an appropriate convexity so that once they have been secured to the tank, they make good contact with the tank surface to ensure satisfactory heat transfer.

A preferred construction is for the plates to be so secured to the tank as to be readily removable or replaceable at any time. Replacement is required when the plate runway has become unsuitable for further use because of wear or other damage.

The plates can be produced from steel plate strips having tempered and quenched yarn runways on one surface thereof. Advantageously, brass strips also can be used for the plates.

Preferably, electric heating elements are disposed in the tank to provide the necessary heat energy. It is relatively easy to maintain a constant temperature by the use of electric heating elements.

Advantageously, to ensure that the heating agent in the tank has a uniform temperature, the heating elements should extend over the entire length of the tank.

Conveniently, the tank is completely surrounded by insulation except for the yarn runways formed by the plates. Such insulation promotes the maintenance of the desired constant temperature.

BRIEF DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENT The invention will be now described in greater detail hereinafter with reference to an embodiment, which is given by way of example only, shown in the drawings wherein:

FIG. 1 is a partly schematic view showing the apparatus and its tank, the latter being in cross-section; and

FIG. 2 is an exploded perspective view showing a tank which has eight yarn-stretching stations whose components are shown separated from one another.

The apparatus shown in FIGS. 1 and 2 for hot-stretching synthetic filaments mainly comprises feed-roller groups 1, a tank 2 and take-up roller groups 3.

The speeds at which the known roller groups 1, 3 rotate are set to provide the required stretching of filaments 4. The tank 2 replaces the conventional irons at the yarn-stretching station and is, in the embodiment shown, prepared from a rectangular tube. Tank 2 has, at the places where yarns run over it, plates 5 consisting of steel plate strips having quenched and tempered yarn runways.

The tank walls can be worked to reduce their thickness slightly at appropriate places to provide a slight convexity of the tank surface at the places where the plates 5 are disposed. The steel plate strips are introduced into the recesses left as a result of such reduction in thickness; such strips are curved correspondingly so as to make intimate contact with the tank wall to promote good heat transfer. Two steel cubes 6 having screwthreads thereon are Welded to the tank 2 at the yarn runways to serve to secure the steel plate strips to the tank wall. Consequently each such strip is maintained in contact with the tank 2 by screws 7 screwed into the cubes 6 and is pressed against the tank wall. The tank 2 can be secured to the frame 8 of a stretch-twisting machine in a simple manner by way of bearing beams 9, the tank 2 being welded thereto.

The tank interior is filled with a liquid heating agent, for instance, a mixture of diphenyl and diphenyl oxide, and heated by electric heating elements 10. The heating elements 10 extend over the whole length of the tank 2 so that the heating agent throughout the tank is heated very uniformly. Consequently, the spaced-apart steel plates are also heated very uniformly and simple temperature supervisory facilities are sufficient to maintain the temperature of the plates 5 constant to within 1 C.

FIG. 2 is an exploded perspective view of the individual parts forming the tank 2. The tank 2 shown is intended for eight yarn runways and has a corresponding number of plates 5. The plates are slightly convex, have two bends at each end, and are formed with bores for the securing screws 7. The plates 5 are introduced into the recesses on the exterior wall of the tank 2 and secured to the cubes 6 welded thereto. The elements 10 are disposed in the tank 2. In the embodiment shown, current is supplied to the elements 10 from an outlet on the left-hand side of the tank 2. A thermostatic control means, generally indicated at 17, is associated with both the tank 2 and the heating elements 10. The thermostatic control means 17 is made of at least one temperature sensing means 18, which may be for example a thermocouple located within the tank for measuring the temperature therewithin, and a switch means 19 for turning on and off the current supplied to the heating elements 10. At the other end of the tank there is a filling tube 11 for the heating agent, the tube 11 having an overflow tube 12. To facilitate assembly of the tank 2, the rear part of the insulation is divided into two separate parts 13, 14. The front of the tank 2 is covered by individual insulating boxes 15 between which the yarn runways are left exposed. Two other insulated boxes 16 serve to insulate the tank end faces.

The tank can be of any length, or a number of small tanks can be placed one beside another on a single stretchtwisting machine, depending upon individual requirements. The main advantage of the tank is that all the plates on it are at the same temperature and, in the event of wear or damage, can be replaced very simply at little cost.

Since all the plates are at the same temperature and have the same drafting surface, the filament quality is uniform even when a number of filaments are stretched one beside another. This uniformity is essential for further processing and ensures that the dyeability of the yarns is uniform.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove.

What is claimed is:

1. In a hot stretching apparatus for synthetic filaments including a plurality of stretching zones each of which comprises:

(1) first roller means for feeding an unstretched synthetic filament,

(2) second roller means for taking up a stretched synthetic filament, said rollers being operated at different peripheral speeds sufficient to stretch said synthetic filament thereby imparting molecular orientation to said filament, and

(3) means for heating said filament disposed between said first and second roller means, comprising a plate providing a running surface disposed for contact with said filament to impart heat thereto and whereon most of said stretching takes place,

the improvement in said heating means which comprises in combination:

(a) a tank disposed transversely to the direction of travel of said filament from said first to said second roller means,

(b) said tank extending transversely across a plurality of said stretching zones,

(c) said tank having a substantially vertical side wall in exterior surface of which is convex only in the area of filament travel in each of said stretching zones,

(d) electrical heating means disposed in said tank through substantially the entire transverse length thereof,

(e) heat transfer medium disposed in said tank to uni formly transfer heat from said heating means to said side wall along the transverse length of said tank,

(f) a plurality of brass strips, each having a convex portion, disposed in laterally spaced apart relationship along said tank,

(g) each of said brass strips being disposed in a stretching zone and having a convex portion the exterior surface of which is adapted for contact with said filaments to impart heat thereto uniformly along said convex portion,

(h) each of said brass strips having a depending portion extending from each end of said convex portion,

(i) means for detachably securing each of said strips to said tank in heat transferring contact with the convex portion of said tank,

(j) means for control of the temperature of said strips constant to Within about 1 C. including a thermocouple disposed within said tank and means for controlling the current supplied to said electric heating means in response to the temperature in said tank, and

(k) means for insulating the areas of said tank between said stretching zones,

whereby uniform stretch quality is imparted to said filaments.

References Cited UNITED STATES PATENTS 2,820,280 1/1958 Benn 2862 2,864,229 12/1958 Seem et a1 2862(X) 2,958,921 11/1960 Gilchrist et al. 2871.3(X) 3,177,931 4/1965 Carruthers 2862(UX) 3,298,430 1/1967 Kodaira 2862(X) 3,319,047 5/1967 Jones, Jr., et al. 28-62(UX) 3,396,524 8/1968 Parker 2862(X) 3,421,192 1/1969 Parker 2862 FOREIGN PATENTS 984,902 3/1965 Great Britain 28-62 26,710 12/1963 Japan 28-62 ROBERT R. MACKEY, Primary Examiner U.S. Cl. X.R. 

